In railway trains,tea/coffee is served in earthen pots and disposal cups made of paper?What are the harms of it?

The two rails of a railway track, insulated from each other and the ground, are connected to a milli voltmeter. What is the reading of the milli voltmeter when a train travels at a speed of 180 km//hours along the track, given that the vertical components of earth's magnitic field is 0.2xx10^(_4) weber//m^(2) & the rails are separated by 1 meter?

A train standing at the outer signal of a railway station blows a whistle of frequency 400 Hz in still air .The train begins to move with a speed of 10ms^(-1) towards the platform. What is the frequency of the sound for an observer standing on the platform?(sound velocity in air = (330ms^(-1)) )

A train,standing at the outersignal of a railway station blows a whistle of frequency 400 Hz in still air. What is the frequency of the whistle for a platform observer when the train approaches the platform with a speed of 10 m s^-1

After the ban on plastic bags, students of one school decided to make the people aware of the harmful effects of plastic bags on environment and Yamuna River. To make the awareness more impactful, they organized rally by joining hands with other schools and distributed paper bags to vegetable vendors, shop keepers and departmental stores. All students pledged not to use polythene bags in future to save Yamuna River. After reading the above passage, answer the following question : What are biodegradable polymers? Give one example?

After the ban on plastic bags, students of one school decided to make the people aware of the harmful effects of plastic bags on environment and Yamuna River. To make the awareness more impactful, they organized rally by joining hands with other schools and distributed paper bags to vegetable vendors, shop keepers and departmental stores. All students pledged not to use polythene bags in future to save Yamuna River. After reading the above passage, answer the following question : What values are shown by the students?

A train,standing at the outersignal of a railway station blows a whistle of frequency 400 Hz in still air. What is the frequency of the whistle for a platform observer when the train. recedes from the platform with a speed of 10 m s^-1 ?